Fibre-based support containing a layer of a functionalized watersoluble polymer, method of production and use thereof

ABSTRACT

A cellulose and/or synthetic fibre-based support of which at least one surface is coated with a layer containing at least one water-soluble polymer comprising hydroxyl or primary-secondary amino functional groups, at least some of which have been functionalized beforehand with at least one organic compound comprising at least one epoxy functional group, and at least one R 1  group wherein R 1  is a vinyl functional group or at least one Si(R 2 ) 3  functional group and wherein R 2 =hydrogen atom, hydroxyl, alkoxy, alkyl, and combinations thereof.

CROSS-REFERENCE

This application is a continuation of commonly owned copending U.S.application Ser. No. 14/235,939, filed Jun. 2, 2014 which is thenational phase application under 35 USC §371 of PCT/FI2012/050744, filedon Jul. 20, 2012, which designated the U.S. and claims priority to EP11175889.2, filed Jul. 29, 2011, the entire contents of each of whichare hereby incorporated by reference.

FIELD OF THE INVENTION

The invention relates to a novel functionalized support based oncellulose and/or synthetic fibres, and to the production method thereof

One of the main areas of application of the present invention relates tosupports that are intended for siliconizing for all self-adhesiveproducts, such as pressure sensitive labels or adhesive tape, for theenvelope industry, weight/price equipment, feminine hygiene products orgraphic applications, for vegetable parchment and greaseproof productsrepresenting a non-limiting selection of applications.

SURVEY OF THE RELATED ART

Supports that are to be siliconized must possess certain propertieswhich are defined in advance according to the final application forwhich they are intended. For instance, in release liner which is one ofthe most important applications, one or two sides of the support arecoated with a silicone film i.e. a release agent. The release agentprovides a release effect regarding any type of sticky materials such asan adhesive, a mastic or dietary pasty (pizza dough for instance). Thus,once they have been siliconized, such supports must guarantee twoprimary functionalities: they must protect the self-adhesive productsbefore they are used and they must be capable of a perfect adhesivetransfer upon removal.

These supports generally consist of a cellulose and/or synthetic fibrebased substrate coated with a layer of water-soluble binding agents,latexes and pigments. They can be produced by many techniques includingcoating, size-press or metering-size-press. One skilled in the art isquite familiar with these coating methods which can also be followed bya calendering or supercalendering step.

The main properties required when manufacturing such cellulose and/orsynthetic fibre fibre-based supports include mechanical strength,silicone anchorage, silicone hold-out and transparency.

Depending on the market that is particularly being targeted, more orless emphasis may be placed on the transparency of the support. Forexample, the weight/price market requires supports that are moretransparent than the market for envelopes.

The silicone hold-out must provide a good surface coverage and mustafford a uniform protection. This objective is generally achieved with aquantity of silicone in the range of 0.5 to 2 g/m². It is important tolimit the quantity of silicone applied without loss of its coveragecapabilities, in order to avoid uneconomical wastages of silicone andconsequent additional costs. Actually, the silicone price has asignificant impact on the total cost of the final products due to therelative high price of the silicone formulation as raw material.Moreover, the catalyst used in the cross-linking reaction of siliconeaccounts for a large part of the overall cost of the siliconeformulation. For instance, in the most part of silicone systems, theplatinum that is used as catalyst cannot be recovered after completionof the reaction.

The cost and the reactivity of the silicones require that the support,on which they are applied, fulfils a certain number of criteria. Firstof all, the chemical structure of the support must not prevent thesilicone system from cross-linking; i.e.—in the case of the platinumbased silicone systems—the polyaddition reaction between the vinylicfunctional groups of the silicone resin and the hydrogen siloxanefunctional groups of the silicone cross-linking agent should not beimpacted. In other words, the support must not inhibit the crosslinkingreaction of the silicone. Next, the support has to provide a perfectanchorage of the silicone to the surface thereof. Furthermore,considering the high cost of silicone, it is important that the amountof silicone deposited on the support is as low as possible. To do this,the support has to form a barrier and thus limit as much as possible thepenetration of the silicone inside the support. Likewise, the surface ofthe support has to be as regular and as smooth as possible in order topermit a homogenous application of the silicone.

In other words, the first problem concerns the development of a supportthat allows simultaneously an efficient anchorage and an optimalcross-linking of the silicone while still reducing as much as possiblethe silicone penetration inside the support.

The siliconizing step does not only depend on the support but also onthe silicone and the cross-linking agent used. The siliconizing methodsare defined according to the silicone cross-linking mode, and these aredivided into two categories, the first being silicones that arecross-linked under UV radiation or electron beams, and the second being“thermal cross-linking” silicones. Since the first category is lessexploitable from both the technical and financial points of view,thermally cross-linked silicones account for the larger market.

Silicones are thermally cross-linked by passing the support, coated insilicone beforehand, through a kiln. The kiln temperature must be suchthat the surface of the support reaches the temperature at which thesilicone cross-linking reaction takes place. In order to enable thecross-linking reaction at a lower temperature, special silicones havebeen developed. They are referred to as “LTC silicones” (low temperaturecuring). Recently, new silicone systems have been commercialized: fastcuring silicone systems, the peculiarity of such a type of silicones isthe fact that the cross-linking reaction takes place properly in thepresence of a lower amount of catalyst (i.e.: Platinum). In the field ofself-adhesives, the term of “curing” refers to the cross-linkingreaction of silicone. The temperatures at which cross-linking occurswith LTC silicones ranges from 60 to 100° C. rather than 110 to 150° C.for conventional silicones. However, up to now the main disadvantage ofusing LTC silicones has concerned the fact that the cross-linkedsilicone presented a very poor anchorage on the support. This anchoragedeficiency of LTC silicones therefore limits their use on a largeindustrial scale.

In the case of release liner applications, there are four main types ofsupport that can be siliconized, these being “coated” papers, vegetableparchment, glassine and greaseproof paper.

“Coated” papers, so called CCK (Clay Coated Kraft), are obtained bydepositing on a cellulose and/or synthetic fibre-based support at leastone coated layer of a mixture containing pigments (clay, calciumcarbonate for example) and binders (starch, polyvinyl alcohol, latex).In order to obtain a satisfactory silicone hold-out, the coated layer isapplied in a quantity of 5 to 20 g/m². The coated support is thencalendered. In general, coated papers are designed particularly forapplications related to envelopes, office labels, hygiene, and graphicapplications.

Vegetable parchment paper is a paper made by passing a waterleaf sheet(unsized paper with a low water resistance), made from chemical woodpulp through a bath of sulfuric acid, or (at times) zinc chloride, underestablished conditions of time, temperature, and the like. The treatedpaper is then washed thoroughly so as to remove the acid or zinc salt,after which it is dried. The chemicals partially dissolve or gelatinizethe cellulose structure of the paper, which is then regenerated when thechemical is diluted by the washing. This forms a very tough, stiff paperwith an appearance somewhat like that of a genuine parchment. Becausepaper treated in this manner has a tendency to become brittle and towrinkle upon drying, it is frequently treated with a plasticizing agent,usually glycerine or glucose.

Such vegetable parchment can be then coated with silicone (generallywater based silicone system), either on one side, or on both side.Silicone coating can occur either on the parchmentizing line, or on anoff-line coater, to produce vegetable parchment for releaseapplications. Due to the fact that such a type of paper is resistantagainst heat and since other substances do not stick onto it, this papercan be used in a variety of applications in packing, storage andrestoration, in composite industry, in dry mounting presses, and as slipsheets for printing.

Glassine is a more refined support than clay coated paper. The processby which it is manufactured differs also in the method used to form thecoating. In fact, the film is formed in a size-press or meteringsize-press coating process and in the final step calendering is replacedby supercalendering. As a result, the product obtained is denser. Italso has greater mechanical resistance and transparency than clay coatedpaper. Glassine is less dimensionally stable than clay coated paper. Themixture used to coat the cellulose support is composed primarily ofwater-soluble binders having a film-forming nature (such as starch,polyvinyl alcohol (PVA) and carboxymethyl cellulose (CMC)), and often ofa viscosifying agent and some additives. The weight of the coating is inthe order of 0.5 to 2 g/m² on each surfaces.

Greaseproof paper is similar to glassine in term of machine process,except that the silicone layer may be applied on paper machine usingwater based emulsions of silicone. The final applications of such a typeof paper include packing, storage and restoration.

The technical problems encountered in the prior art and in the researchare mainly associated with the improvement in the anchorage of thesilicone on the support, in avoiding the inhibition of the cross-linkingreaction of silicone and in reducing the quantities of silicone andcatalyst (i.e.: Platinum) applied on the support for relevant reasonsconcerning the cost saving.

In the past, any changes to the siliconizing method, in particular byreducing the quantity of the catalyst used or by use of LTC and fastcuring silicones in large amounts, have resulted in difficultiesregarding the anchorage of silicone. Actually, it has been observed thatthe main limitating step for improvement in the siliconizing processconcerns the poor anchorage of the silicone on the substrate. Recently,the producers of substrates to be siliconized, tried to solve theanchorage problems by focusing their research in the production ofsupports able to interact or react with the silicone system; in otherwords, they tried to convert the fibre support from an inert substrateto an “active” or “reactive” substrate for the silicone.

In order to “activate” the substrate regarding silicone, researcherstried to apply onto the substrate the functional groups involved in thecross-linking reaction of silicone: vinyl, silicone hydride and silanolfunctionalities.

Thanks to this approach, the silicone should be able to react not onlywith itself but with the substrate as well, giving the anchorage to thesubstrate. It has been demonstrated that this approach should work butthis concept came up against difficulties in the production of“activated” substrates and products with such a type of characteristicsare not yet available on the market.

Document WO2005/071161 describes a glassine that is coated with standardcoating formulations. This cellulose-based support is thenfunctionalized by grafting directly onto it an organic moleculecontaining a vinylic function and an acid halide function. The hydroxylfunctionalities of the substrate react with the acid halide function ofthe organic molecule to create covalent bonds between them. Thechain-terminal vinylic function enables good anchorage and excellentcross-linking of the silicone due to the formation of covalent bondsbetween the support and the silicone. This siliconizing step of thisglassine may also be performed with LTC silicones. The results obtaineddemonstrate an improvement of the anchorage of silicone on the support.

The grafting reaction reported in document WO2005/071161 can beperformed either in an organic solvent process or by applying directlythe pure reactant onto the substrate. However, the grafting cannot becarried out in a water based process due to the fact that such a type oforganic molecules are very sensitive to water. Actually, the acid halidefunction (used as reactive function for the grafting reaction) reactswith water to form chemicals that do not react with the substrate. As aresult, such a type of organic molecules cannot be used in conventionalwater-based coating of substrates. Another drawback concerns theproduction of acids (hydrochloric acid, hydrobromic acid, etc.) asby-products during the grafting reaction. The formation of volatile andstrong acids during the process causes serious problems regarding thesafety of the employees, the environmental system and problems ofcorrosion of the industrial machines.

Although using an organic solvent based process to apply the graftingmolecule on the substrate could solve the problems related to theinhibition of the grafting molecule, this approach would significantlyincrease the problematic aspects related to safety, environmental andcorrosive issues.

On the other hand, the coating of the pure grafting molecule directlyonto the substrate could solve the problems of inhibition of thereactant, but in this case as well, the man in the art is facing safetyand corrosive issues. Moreover, up to now, the technology to apply verylow amount of such organic molecules on an industrial machine has beenmissing.

Document WO2009/147283 describes a glassine that has been coated with amodified compound i.e. a functionalized polymer. In this case, thefunctionalization is carried out off-line from the industrial machineand the functionalized compound is applied by coating. Thefunctionalization of the compound is carried out by using one of thefollowing grafting functionalities: halogenic alkene, carboxylic acid,acid chloride, acid anhydride or acid ester. Even though thefunctionalized polymers could be applied onto the substrate by using awater-based process, the grafting reactions cannot be performed in wateras solvent.

In fact, in the case of halogeno alkenes or acid chloride as reactivefunctional groups, they readily react with water to afford functionalgroups that do not react with the polymer. Another drawback is theproduction of hydrochloric acid as a by-product during the graftingreaction.

In the case of carboxylic acids, acid anhydride or acid ester asreactive functional groups, the reaction of a chemical containing one ofthese functional groups with the polymer would lead to the formation ofa molecule of water. However, it is well known in organic chemistry thatsuch a type of reactions are reversible and give a chemical equilibriumbetween reactants and products. If the solvent is water, the equilibriumis mainly shifted to the direction of the reactants (Le Chatelier'sprinciple). As a result, in water, this reaction does not occur or, ifit occurs, it affords a very low yield of reaction.

Although the grafting technology reported in these prior art documentsare carried out in organic solvents (anhydrous organic solvents in thecase of halogenic alkene or acid chloride as reactive functionalgroups), the use of organic solvents for the grafting reaction presentsseveral disadvantages. In fact, in addition to safety and environmentalissues, the cost of the organic solvent based grafting technology isvery high due to the multi-steps process required. In particular, thepolymer has first to be solubilized in the organic solvent, the solventis then evaporated at the end of the reaction. The modified polymer canalso be precipitated with a non-solvent, the solvent being purified orsubstituted for the next step, and the obtained grafted polymersolubilized again in water to be then coated on the industrial machine.Such a type of multi-steps process makes the technology not competitivein comparison with the possible benefits in performances of the finalproduct for the silicone.

The problems that the present invention intends to solve relate to animproved support that does not suffer from the drawbacks described inthe preceding.

BRIEF DESCRIPTION OF THE INVENTION

The present invention suggests to carry out the grafting of the polymerin water as solvent, and then to coat the functionalized polymers ontothe cellulose and/or synthetic fibre substrate by using a water basedcoating solution. Thanks to the chemistry related to the presentinvention, the reaction of polymer grafting is carried out in a waterbased process as well, before the coating on the support. In the presentinvention, the organic molecule used comprises an epoxy function,optionally in the form of a chloro-hydrin, as reactive functional groupfor the polymer grafting. In addition to the epoxy functionality, theorganic molecule comprises at least one vinylic or one silicone hydrideor one silanol functional group. The linkage between the water solublepolymer and the organic molecule depends on the polymer involved in thereaction. The reaction does not form water as by-product of the reactionand it is performed in water as solvent with a high yield of reaction.

The water soluble polymer functionalized with the method reported in thepresent invention is then coated onto a support based on the celluloseand/or synthetic fibre substrates, using any kind of surface treatmentin the industry.

As soon as the functionalized water soluble polymer is applied onto thesubstrate, vinylic or silicone hydride or silanol functionalities arepresent on the surface of the substrate. The presence of the vinylicfunction or silicone hydride or silanol functionality enables thesilicone to react with the substrate in the siliconizing stagegenerating covalent bounds between the silicone layer and the substrate.Thanks to the covalent boundings the adhesion of the silicone layer issignificantly improved and no inhibition of the silicone cross-linkinghas been observed.

The present invention provides to the substrate to be siliconizedseveral improved characteristics obtained by using a safety,environmental friendly and cheap process; representing a significantcontribution to the search for sustainable technical and industrialsolutions.

The present invention provides a new approach which improves celluloseand/or synthetic fibre-based supports that are intended to be coveredwith a silicone film. Thanks to the present invention, the fibre-basedsupport is improved by using a complete process that can be solely waterbased. In fact, a water soluble polymer is modified by a chemicalreaction using water as solvent. The resulting grafted water solublepolymer is then coated on a substrate by using any water based methodsknown to one skilled in coating processes.

The resulting products exhibit an improved cross-linking of the siliconeand an enhanced anchorage of the silicone on the substrate as comparedto the prior art supports. The improvement of the cross-linking ofsilicone and the enhancement in silicone anchorage, enables thepossibility to reduce the amount of catalyst to be used in the siliconeformulation (i.e.: Platinum), to maintain the silicone adhesionproperties when the product is subject to severe humid conditions, andalso to reduce the curing time of the silicone during the siliconizationstep (i.e.: it gives the possibility to increase the speed of thesiliconizing machines without any arrangements of the industrialmachines).

More precisely, the subject matter of the invention concerns a celluloseand/or synthetic fibre-based support of which at least one surface iscoated with a layer containing at least one water-soluble polymercomprising hydroxyl or primary-secondary amino functional groups, atleast some of which have been functionalized beforehand with at leastone organic compound;

wherein said organic compound contains:

-   -   at least one epoxy functional group, and    -   at least one R¹ group wherein R¹ is a vinyl functional (CH₂═CH—)        group or at least one —Si(R²)₃ functional group and wherein        R²=hydrogen atom, hydroxyl, alkoxy, alkyl, and combinations        thereof.

As already said, in the support according to the present invention, thehydroxyl and/or primary-secondary amino functional groups of thewater-soluble polymer have been functionalized beforehand with at leastone organic compound.

In a preferred embodiment, the epoxy functional group of said organiccompound corresponds to a saturated three-membered cyclic ether.

The term cellulose fibre-based support is understood to mean a supportthat contains cellulose fibres that have been more or less adapted inproportions ranging from 50 to 99% by weight for purposes of theirdesired characteristics (density, transparency, mechanical properties).

The term synthetic fibre-based support, commonly called nonwoven, isunderstood to mean as a sheet or web structures bonded together byentangling fibre or filaments by a mechanical, thermal or chemicalprocess. Nonwovens are flat, porous sheets that are made directly fromseparate fibres (wetlaid process) or from molten plastic particles(spundbound, meltblown or electrospinning processes). Typical fibresused in the production of nonwovens are made of: polyester (for example:polyethylene terephthalate, polybutylene terephthalate, polylacticacid), polyolefines (for example: polypropylene, polyethylene),polyamides (for example: nylon 6, 6-6, 12, 6-12), polyphenylene sulfide,polycarbonate, viscose and fibreglass.

Substrates of cellulosic and synthetic fibres can be produced andadapted in relative proportions ranging from 1 to 99% by weight forpurposes of their desired characteristics. For instance, someapplications may involve or require the addition of small amounts ofsynthetic fibres to the cellulose as a reinforcement material.

In a particular embodiment, the support is a cellulose fibre-basedsupport.

The coating layer that contains the functionalized water soluble polymeris designed to afford silicone barrier properties to the surface of thefibre-based support.

When the water soluble polymer contains hydroxyl functional groups, thelinkage between the polymer and the organic molecule is made through anether bond with a hydroxyl functionality in position 2 (i.e.:2-hydroxyether) (as in FIG. 1).

When the water soluble polymer contains primary or secondary aminofunctional groups, the linkage between the polymer and the organicmolecule is an alkylated amine (secondary or tertiary amine) with ahydroxyl function in position 2 (i.e.: 2-hydroxyamine) (as in FIG. 2).In a particular embodiment, the water soluble polymer may comprise bothhydroxyl and primary-secondary amino functional groups (i.e.: chitosan).

In both cases (OH and NH/NH₂ containing polymers), the chemical reactioninvolved is an alkylation reaction where no other by-products areproduced during the reaction (i.e.: water is not produced).

Additionally, the coating layer comprising the water-soluble polymer maycontain at least one functionalized water-soluble polymer and at leastone water soluble polymer that has not been functionalized. As a result,functionalized and unfunctionalized hydroxyl or amino functional groupsmay be contained in the same water-soluble polymer, or they may becontained in a mixture of a least two water-soluble polymers comprisingdifferent hydroxyl or amino functional groups.

Furthermore, the coating layer that contains the functionalizedwater-soluble polymer may also contain other water-soluble binders,conventional additives, pigments and latexes. Depending on the nature ofthe water soluble polymer, a suitable crosslinker can be advantageouslyadded in the formulation in order to render the polymer water insolubleafter the application of the polymer on the substrate and the drying ofthe product. In fact, once the coated support is dried, the watersoluble polymer can become water insoluble due to its cross-linking. Theskilled man in the art knows that the hydrosoluble properties of apolymer can be affected when a crosslinker is added.

Interestingly, when the organic molecule is not water soluble, thegrafting reaction can still occur in water. In fact, by vigorousstirring, it is possible to create an emulsion of the organic moleculein the water solution and the grafting reaction occurs even if thepolymer and the reactant are not in the same phase.

In a preferred embodiment of the invention, the water-soluble polymercontaining hydroxyl functional groups can advantageously be chosen fromthe group comprising natural and modified polysaccharides such asstarch; CMC (carboxymethyl cellulose); alginate; chitosan, pectine,chitin, glycogen, arabinoxylane, cellulose and synthetic polymers suchas poly(vinyl alcohol); hydrolysed or partially hydrolysed copolymers ofvinyl acetate, which may be obtained for example by hydrolysingethylene-vinyl acetate (EVA) or vinyl chloride-vinyl acetate, N-vinylpyrrolidone-vinyl acetate, and maleic anhydride-vinyl acetatecopolymers.

In a preferred embodiment, the water-soluble polymer containing hydroxylfunctional groups is advantageously starch.

In another preferred embodiment, the water-soluble polymer containinghydroxyl functional groups is advantageously PVA.

In a preferred embodiment of the invention, the water-soluble polymercontaining primary-secondary amino functional groups can advantageouslybe chosen from the group comprising polyethyleneimine; polyallylamine;chitosan; polyacrylamide; partially or totally hydrolizedpolyacrylamide; partially or totally hydrolized polyvinylamine,polyamines based on amino-ethyl-piperazine; and in general big moleculescontaining aliphatic or aromatic polyamino functional groups as forexample spermidine, spermine, diethylenetriamine, triethylenetetramineand tetraethylenepentamine. This water-soluble polymer containing aminofunctionalities is advantageously polyethyleneimine, polyallylamine andpartially or totally hydrolized polyvinylamine.

Typically, the water soluble polymers that are grafted correspond to amolecule containing at least one element from the group of C, H, N, O,non-metals such as the halogens, Si, S, P, metals such as Na, Li, K, Mg,Pb, etc.

The molecular weight of the water soluble polymer comprisingprimary-secondary amino or hydroxyl functional groups preferably rangesfrom 1,000 to 1,000,000 a.m.u, advantageously from 50,000 to 150,000a.m.u.

As already stated, the organic molecule enabling the grafting of thewater soluble polymers contains at least one epoxy functionality(—CH—O—CH₂) as well as at least one functional group among vinylic(—CH═CH₂), silicone hydride (Si—H), and silanol (Si—OH) groups. Theepoxy group enables the organic molecule to be grafted onto thewater-soluble polymer containing hydroxyl or primary-secondary aminofunctions by an alkylation reaction.

In the grafting reaction reported in the present invention, the organicmolecule can contain, in addition to the epoxy functional group, silanolgroups (Si—OH) that are able to react with silicone after siliconizing.It is familiar to one skilled in the art that the silanol functionalitycan be formed from the hydrolysis of alkoxylated silanols (Si—O—R*,where R* can be a methyl, ethyl, propyl, isopropyl, butyl, isobutyl etc.functionality). The reaction concerns hydrolysis of alkoxylated silanolsin water; which can be catalysed in acid or basic pH. This reactionleads to the formation of by products such as alcohols (methanol,ethanol, propanol, isopropanol, butanol, isobutanol etc.). Organicmolecules comprising silanol groups resulting from the in situhydrolysis of alkoxylated silanol groups (Si—OR*) exhibit the samereactivity as organic molecules comprising silanol groups (Si—OH) thattherefore do not require any in situ hydrolysis. However, over time,alkoxylated silanols are more stable than silanols, and thereforeprovide a more convenient raw material reactant for the graftingreaction of the water soluble polymer.

With regards to the polymer grafting reaction involving an alkylation,carrying out the reaction in basic or acidic conditions can catalyze thealkylation. In fact, aqueous acidic conditions can enhance theactivation of the oxygen atom of the epoxy group while basic conditionscan enhance the activation of the nucleophile that reacts with the epoxygroup. Basic pH conditions are usually preferred to the acid conditionssince it decreases the eventual formation of side-products (such asdialcohols resulting from the reaction of the epoxy group with water andsubsequent inactivation of the organic molecule for the graftingreaction). Moreover, basic pH conditions are preferred due to the natureof some base polymers, such as polysaccharides, which are more stable inbasic conditions compared to acid conditions. In fact, in acid pHconditions, polysaccharides can undergo hydrolysis reaction andtherefore exhibit different polymer properties, or be definitelydamaged.

After the grafting reaction of the water soluble polymer with theorganic molecule, such a functionalized water soluble polymer can thenbe coated onto the fibre-based support using any kind of surfacetreatment from the coating technology. The coating layer is layed downonto the fibre-based support, thereby producing, in a single and rapidstep on the industrial machine, a support exhibiting the desiredfunctionality and a barrier between the silicone and the support.

Therefore, the product produced by the described process presents at theweb surface vinylic or silicone hydride or silanol functionalities whichenable a better anchorage of the silicone during the subsequentsiliconizing step.

For the sake of simplicity, the water-soluble polymer containinghydroxyl or primary-secondary amino functionalities will be referred toby the abbreviation “PH” in the following. The terms “functionalized PH”will be used to denote the products of the reaction between PH and theorganic molecule described in the preceding.

The formula of the organic molecule selected to functionalize thewater-soluble polymer containing hydroxyl or primary-secondary aminofunctionalities is advantageously one of the following:

H₂C—O—CH—(R)—CH═CH₂

H₂C—O—CH—(R)—Si—(R²)₃

wherein R=linear, branched and/or cyclic carbon —(C)_(x)— chain or apolydimethylsiloxane chain (—O—Si(CH₃)₂—)_(y) or the combination of thetwo (—C—)_(z)—(—O—Si(CH₃)₂—)_(j) chains that may also containsheteroatoms (X) as part of the chain structure —C—X—C— or as side groupof the chain structure —C(X)—;

and wherein R²=hydroxyl (—OH); hydrogen atom (H); alkyl; alkoxy such asfor example methoxy (—O—CH₃), ethoxy (—O—CH₂—CH₃), propyoxy(—O—CH₂—CH₂—CH₃)); and combinations thereof.

In a preferred embodiment, x is comprised between 1 and 25, and moreadvantageously between 5 and 12.

In a preferred embodiment, y is comprised between 1 and 15, and moreadvantageously between 1 and 8.

In a preferred embodiment, z is comprised between 1 and 15, and moreadvantageously between 1 and 8.

In a preferred embodiment, j is comprised between 1 and 15, and moreadvantageously between 1 and 8.

In the two formulae above, “C—O—C” represents a saturated three-memberedcyclic ether.

In a preferred embodiment, the —Si(R²)₃ group can be chosen from thegroup comprising —Si(OH)₃, —Si(OH)₂(CH₃), —Si(OH)(CH₃)₂, —Si(H)(CH₃)₂,—Si(H)₂(CH₃), —SiH₃, —Si(OR³)₃, —Si(OR³)₂(CH₃), —Si(OR³)(CH₃)₂, whereinR³ are groups chosen from —CH₃, —CH₂—CH₃, —(CH₂)₂—CH₃, —CH(CH₃)₂,—(CH₂)₃—CH₃, —CH₂—CH(CH₃)₂, —(CH₂)₄—CH₃, —(CH₂)₂—CH(CH₃)₂, —C₆H₆ andcombinations thereof.

In a preferred embodiment of the invention, the organic molecules usedfor the grafting reaction of the water soluble polymer can be preferablyone of the following compounds: 2-vinyloxirane, 1,2-epoxy-4-pentene1,2-epoxy-5-hexene, 1,2-epoxy-6-heptene, 1,2-epoxy-7-octene,1,2-epoxy-8-nonene, 1,2-epoxy-9-decene, 1,2-epoxy-10-undecene,1-allyloxy-2,3-epoxypropane, 1-allyloxy-3,4-epoxybutane,1-allyloxy-2,3-epoxypentane, 1-allyloxy-2,3-epoxyhexane,1-allyloxy-2,3-epoxyheptane, 1-allyloxy-2,3-epoxyoctane,1-allyloxy-2,3-epoxynonane, 1-allyloxy-2,3-epoxydecane,1-allyloxy-2,3-epoxyundecane, glycidoxypropyl trimethoxysilane,glycidoxypropyl triethoxysilane, glycidoxypropyl trisiloxane.

Said organic molecule is advantageously 1,2-epoxy-9-decene or1-allyloxy-2,3-epoxypropane.

In a preferred embodiment, said organic molecule represents between 0.1%and 20% by weight of the weight of the PH, more advantageously between0.1% and 10% and even more advantageously between 0.1% and 5%. Even moreadvantageously, the organic molecule represents 1% by weight of theweight of the PH. The control of the grafting rate thus enables thesilicone anchorage to be controlled afterwards, and this is assisted bythe presence of the vinylic or silicone hydride or silanolfunctionality.

The functionalized PH preferably accounts for at least 1% by weight ofthe layer coated onto the cellulose and/or synthetic fibre-basedsupport, advantageously at least 5%, and even more advantageouslybetween 20 and 100%.

The cellulose layer that forms the support according to the inventiontypically exhibits a weight ranging from 30 to 160 g/m², preferably from55 to 140 g/m², and most advantageously in the order of 58 g/m². In aparticular embodiment, the weight of the support corresponds to theweight of the fibres. At least one surface of this support is coatedwith the described coating layer in a quantity of 0.2 to 20 g/m²,preferably 1 g/m².

The support according to the present invention may be prepared by thefollowing method:

-   -   formation of a cellulose and/or synthetic fibre-based sheet;        with or without a parchementizing process.    -   functionalization of at least one water soluble polymer        comprising hydroxyl or primary-secondary amino functional        groups, by grafting at least one organic molecule comprising at        least one epoxy group and at least one IV functional group        wherein R¹ can be chosen from a vinyl group, or at least one        —Si(R²)₃ functional group and wherein R²=hydrogen atom,        hydroxyl, alkoxy, alkyl, and combinations thereof. Said organic        molecule is able to form covalent bonds with the hydroxyl or        primary-secondary amino functional groups of the PH.    -   coating the cellulose and/or synthetic fibre support, by methods        known to one skilled in the art, with at least one        functionalized PH; this step will advantageously be carried out        at a temperature between 20 and 95° C., preferably between 50        and 70° C.    -   calendering or supercalendering the support if required.

In a particular embodiment of the invention, a chloro-hydrin compoundcan be used as precursor of the organic molecule. Indeed, thechloro-hydrin compound reacts in basic conditions to form an epoxycompound. The water soluble polymer is therefore still grafted with amolecule containing an epoxy functional group. The conversion from thechloro-hydrin functional group to the epoxy group can be carried outbefore or during the grafting reaction.

Still according to this particular embodiment, an organic moleculecomprising an epoxy group can be obtained from a compound containing achloro-hydrin group, in aqueous alkaline conditions. In fact, thechloro-hydrin easily reacts with water in alkaline conditions. However,it can be converted to epoxy and therefore be “activated” by apre-chemical reaction. The chloridric acid which is a by-product of thispre-reaction and it can be converted to a salt (for example sodiumchloride, thanks to the alkaline conditions obtained by the addition ofsodium hydroxide). The organic molecule comprising an epoxy group andobtained from the chloro-hydrin precursor exhibits the same reactivityas an organic molecule comprising an epoxy group that does need to bepre-activated. The chloro-hydrin precursor can be advantageous in thatit is more chemically stable over time and it exhibits lower toxicity ascompared to epoxy compounds.

According to a preferred method, the PH is functionalized at atemperature between 20 and 95° C., preferably between 80 and 95° C., inaqueous phase, and eventually in the presence of an organic or aninorganic acid or base as catalyst. In fact, adding an organic or aninorganic acid or base may be necessary when the PH is not alreadyacidic or basic.

Coating techniques known to one skilled in the art further includesize-press, metering-size-press, foulard coating, rod coating,“Champion” bar coating, “Meyer” bar coating, air-knife coating, gravurecoating, scraper blade coating, sliding blade coating, single- andmultilayer curtain coating, reverse roll coating, spray coating,atomisation coating, liquid application system (LAS) coating, kisscoating, foam coating, and any surface coating application process.

The present invention relates as well to a cellulose and/or syntheticfibre-based support of which at least one surface is coated with a layercontaining at least one water-soluble polymer comprising hydroxyl orprimary-secondary amino functional groups, at least some of which havebeen functionalized beforehand or after the step of coating with atleast one organic compound. Said organic compound contains:

-   -   at least one epoxy functional group, and    -   at least one R¹ group wherein R¹ is a vinyl group or at least        one Si—(R²)₃ functional group and wherein R²=hydrogen atom,        hydroxyl, alkoxy, alkyl, and combinations thereof.

Additionally, the present invention concerns the process associated tothis support.

Generally, a cellulose and/or synthetic fibre-based support according tothe invention will be treated in a siliconizing step for use insupports, for instance, for self-adhesive labels, adhesive tapes andvegetable parchment for example. It will be siliconized by any of themethods known to one skilled in the art.

In general, the present invention consists in the functionalization of awater soluble polymer containing amino or hydroxyl functional groupswith a molecule having an epoxy function by using a water based process,and in applying the functionalized polymer on a cellulose and/orsynthetic fibre-based support by a water based coating technique. Thepresent invention is in contrast to the prior art; which consisted ingrafting a molecule directly (or dissolved in organic solvents) onto thecellulosic support or in the pre-grafting a molecule on a polymers usingreactions in organic solvents and then coating the resulting graftedpolymers on the cellulosic substrate.

EXEMPLARY EMBODIMENTS OF THE INVENTION

The invention itself and the advantages that it offers will be explainedin greater detail in the following description of exemplary embodimentsand with reference to the following figures.

FIG. 1 represents the alkylation reaction, in an aqueous medium at abasic or acid pH, between a water soluble polymer containing hydroxylfunctionalities and an organic molecule comprising both an epoxyfunction and a functional group among, for instance, Si—H, Si—OH, orvinyl. In this particular case, starch is the water soluble polymercontaining hydroxyl functionalities while the molecule having an epoxyfunctionality refers to the general formula: H₂C—O—CH—(R)—R¹.

FIG. 2 represents the alkylation reaction, in an aqueous medium at abasic or acid pH, between a water soluble polymer containing primaryand/or secondary amino functionalities and an organic moleculecomprising both an epoxy function and a functional group among, forinstance, Si—H, Si—OH, or vinyl. In this particular case,polyethyleneimine is the water soluble polymer containing primary andsecondary amino functionality while the molecule having an epoxyfunctionality refers to the general formula: H₂C—O—CH—(R)—R¹.

EXAMPLES Method for Preparing the Glassine According to the Invention:

A sheet consisting of 100% cellulose fibres is prepared by methods knownto one skilled in the art. The support used in the examples is thecommercial product Silca Classic Yellow 59 g/m² (from Ahlstrom); for theproduction of the samples described in the examples, the support has notbeen coated with the standard formulation but with the formulationsreported in the examples 1 and 2. In the case of the standard paper, thecommercial grade Silca Classic Yellow has been used as such.

Off-line from the industrial machine, the water soluble polymercontaining primary-secondary amino or hydroxyl functionalities isfunctionalized with an organic molecule by using the methods of examples1 and 2. After the functionalization reaction, the polymer solution canbe mixed with other products commonly used in this application (forexample: clays, pigments, latexes, polymers and/or additives), dilutedwith water to the desired solid content and sent to the industrialmachine for the coating step.

The mixture containing the functionalized water soluble polymer is thenapplied to a surface of the support by coating (1 g/m²), preferably bymetering-size-press.

The support is then dried, remoisturized, and super-calendered.

Example 1 Functionalization Reaction of a Water Soluble PolymerContaining Primary and/or Secondary Amino Functionalities andPreparation of the Coating Recipe

In the present example, polyethyleneimine is the polymer containingprimary and/or secondary amino functionalities since it contains bothfunctionalities on the same polymer structure.

The commercial polyethyleneimine Polymin P (from Base is delivered as awater solution with a solid content of 50% w/w. In order to decrease theviscosity of the solution, Polymin P is diluted with water at a solidcontent of 20%. For the grafting reaction, an amount of 2% w/w of pure1,2-epoxy-9-decene (from Sigma-Aldrich), compared to the weight of dryPolymin P, is slowly added to the polymer solution under vigorousstirring. The organic molecule 1,2-epoxy-9-decene is a liquid which isnot soluble in water, so a vortex is required to create an emulsion of1,2-epoxy-9-decene in the polymer solution, forming a cloudy solution.Due to the fact that Polymin Pin solution already has a pH between 11and 13, the addition of a base in order to increase the pH to catalyzethe reaction is not required. The solution is heated to 90° C. andmaintained at this temperature under stirring for one hour.Subsequently, the pH of the solution is neutralized by addition of awater solution of sulphuric acid. Afterwards, 20% w/w of CMC and 5% w/wof glyoxal compared to the weight of Polymin P are added to thesolution. The solution is then diluted with water to a final solidcontent of 8% w/w. Finally, the solution is transferred to the coatingapparatus for the coating step. CMC is added in the coating formulationas a viscosity modifier to improve the film forming properties and thewater retention of the coating formulation. Glyoxal is added as across-linking agent for the coating formulation.

Example 2 Functionalization Reaction of a Water Soluble PolymerContaining Hydroxyl Functionalities and Preparation of the CoatingRecipe

In the present example, PVA, Celvol 20/99 (Celanese), is therepresentative polymer containing hydroxyl functionalities. Celvol 20/99is delivered as a powder. A dispersion of PVA is produced in water byvigorous stirring. It is then heated up to 95° C. in order to completelydissolve PVA in water. A clear solution with a solid content of 12% isobtained. A solution of sodium hydroxide is added to the PVA solution inorder to reach a pH value between 11 and 13. For the grafting reaction,an amount of 2.5% w/w of pure 1,2-epoxy-9-decene (from Sigma-Aldrich),compared to the weight of dry Polymin P, is slowly added to the polymersolution under vigorous stirring. The organic molecule1,2-epoxy-9-decene is a liquid which is not soluble in water, so avortex is required to create an emulsion of 1,2-epoxy-9-decene in thepolymer solution, forming a cloudy solution. The solution is heated to90° C. and maintained at this temperature under stirring condition forthree hours. Subsequently, the pH of the solution is neutralized byaddition of a water solution of sulphuric acid. Afterwards, 10% w/w ofCMC and 5% w/w of glyoxal compared to the weight of PVA are added tosolution. The solution is then diluted with water to afford a finalsolid content of 8% w/w. Finally, the solution is transferred to thecoating apparatus for the coating step.

Example 3 Silicone Anchorage of Low Temperature Curing (LTC) SiliconeSystems

Standard glassine (STD) and the glassine produced by the methodsreported in examples 1 (EX1) and 2 (EX2) have been siliconized with LTCsilicones. The silicone anchorage results have been compared. In orderto assess the silicone anchorage, a standard test called rub-off testhas been performed; this test is an abrasion test in which a sample ofsiliconized paper, pressed under a weight, is dragged on an abrasivetextile. The silicone layer at the surface of the sample can be removedby the rubbing. By measuring the amount of silicone onto the samplesbefore and after the rub-off test, it is possible to obtain a percentageof silicone that remains on the samples. The rub-off percentage 0%indicates that all the silicone has been removed from the sample, verypoor adhesion; the rub-off percentage 100% indicates that all thesilicone remained on the sample, the adhesion is ideal. For the releaseapplication, the rub-off value of 75% is commonly considered as thebottom limit for silicone anchorage. The following silicone formulationhas been used in this example:

LTC silicone formulation bath:

Polymer: D920 (from Wacker)—18.07 g

Cross-linking agent: XV 525 (from Wacker)—1.43 g

Catalyst: C05 (i.e.: Platinum based from Wacker)—2.14 g

Deposit: 0.9 g/m²

Cross-linking for 30 seconds at 80° C. in a ventilated drying kiln

Table 1 shows that STD has a rub-off value of 18% (very poor adhesion ofthe silicone), whereas EX1 and EX2 have respectively rub-off values of96% and 97% (both samples have very good adhesion properties for LTCsilicone systems). So, in the case of standard glassine the LTC siliconecannot be used due to the poor adhesion of the silicone system to thesubstrate; on the contrary, LTC silicone systems can be used on glassineproduced by the methods reported in the present invention.

TABLE 1 Sample STD EX1 EX2 Rub-off value 18% 96% 97%

Example 4 Silicone Anchorage Dependence on the Amount of Catalyst (i.e.:Platinum) in the Silicone Formulation

For thermal cured silicone systems used in release industry, thecatalyst used is an organometallic compound of platinum. Due to the highprice of platinum, there is a strong interest in reducing its amount inthe silicone formulation. The first problem observed when a reducedamount of catalyst is used is a poor anchorage of the silicone to thesubstrate. Standard glassine (STD) and the glassine produced by themethods reported in examples 1 (EX1) and 2 (EX2) have been siliconizedwith a standard silicone formulation by using two different amounts ofcatalyst in the silicone formulation, and the silicone anchorage ondifferent substrates has been tested. In order to evaluate the siliconeanchorage, the rub-off test (described in example 3) has been performed.For the tests the following silicone formulations have been used:

Standard silicone formulation bath:

Polymer: 11367 (from Bluestar)—50 g

Cross-linking agent: 12031 (from Bluestar)—2.9 g

Catalyst (60 ppm Platinum): 12070 (from Bluestar)—1.56 g; or (30 ppmPlatinum): 12070-0.78 g

Deposit: 0.9 g/m²

Cross-linking for 10 seconds at 160° C. in ventilated drying kiln

As it is possible to observe in table 2, an satisfactory rate ofsilicone anchorage is obtained for all samples when the siliconeformulation contains 60 ppm of platinum. On the contrary, when theamount of platinum is decreased to 30 ppm, the silicone anchorage ofsamples EX1 and EX2 remains very good but the anchorage of STD is poor.

TABLE 2 STD EX1 EX2 Rub-off 90% 95% 98% (60 ppm of Platinum) Rub-off 54%91% 93% (30 ppm of Platinum)

1. A coated cellulose and/or synthetic fibre-based support, wherein thecoated fibre-based support comprises: a cellulose and/or syntheticfiber-based support sheet, and a coating layer on at least one surfaceof the support sheet, wherein the coating layer comprises at least onewater-soluble polymer comprising hydroxyl or primary-secondary aminofunctional groups, wherein at least some of the hydroxyl orprimary-secondary amino functional groups on the polymer have beenfunctionalized with at least one organic compound before the polymer iscoated onto the at least one surface of the support, and wherein the atleast one organic compound contains: (i) at least one epoxy functionalgroup, and (ii) at least one R¹ group wherein R¹ is a vinyl functionalgroup or at least one Si(R²)₃ functional group, where R² is a groupselected from the group consisting of hydrogen, hydroxyl, alkoxy, alkyl,and combinations thereof, wherein the at least one organic compound isgrafted onto the water-soluble polymer via the at least one epoxyfunctional group by an alkylation reaction.
 2. The coated celluloseand/or synthetic fibre-based support as recited in claim 1, wherein thecellulose and/or synthetic fibre-based support sheet is a cellulosesupport sheet.
 3. The coated cellulose and/or synthetic fibre-basedsupport as recited in claim 1, wherein the water-soluble polymer havinghydroxyl functional groups is selected from the group consisting ofstarch, carboxymethyl cellulose (CMC), alginate, chitosan, pectine,chitin, glycogen, arabinoxylane, poly(vinyl alcohol), and hydrolysed orpartially hydrolysed copolymers of vinyl acetate.
 4. The coatedcellulose and/or synthetic fibre-based support as recited in claim 1,wherein the water-soluble polymer having hydroxyl functional groups isstarch.
 5. The coated cellulose and/or synthetic fibre-based support asrecited in claim 1, wherein the water-soluble polymer havingprimary-secondary amino functional groups is selected from the groupconsisting of polyethyleneimine; polyallylamine; chitosan;polyacrylamide; partially or totally hydrolyzed polyacrylamide;partially or totally hydrolyzed polyvinylamine and polyamines based onamino-ethyl-piperazine.
 6. The coated cellulose and/or syntheticfibre-based support as recited in claim 1, wherein the organic moleculecorresponds to a molecule according to the formula H₂C—O—CH—(R)—CH═CH₂or H₂C—O—CH—(R)—Si—(R²)₃, wherein R is a linear, branched and/or cycliccarbon chain or a polydimethylsiloxane chain that may containheteroatoms, and R² is selected from the group consisting of hydrogen,hydroxyl, alkoxy, alkyl and combinations thereof.
 7. The coatedcellulose and/or synthetic fibre-based support as recited in claim 1,wherein the organic molecule is a molecule selected from the groupconsisting of 2-vinyloxirane, 1,2-epoxy-4-pentene 1,2-epoxy-5-hexene,1,2-epoxy-6-heptene, 1,2-epoxy-7-octene, 1,2-epoxy-8-nonene,1,2-epoxy-9-decene, 1,2-epoxy-10-undecene, 1-allyloxy-2,3-epoxypropane,1-allyloxy-3,4-epoxybutane, 1-allyloxy-2,3-epoxypentane,1-allyloxy-2,3-epoxyhexane, 1-allyloxy-2,3-epoxyheptane,1-allyloxy-2,3-epoxyoctane, 1-allyloxy-2,3-epoxynonane,1-allyloxy-2,3-epoxydecane, 1-allyloxy-2,3-epoxyundecane,glycidoxypropyl trimethoxysilane, glycidoxypropyl triethoxysilane, andglycidoxypropyl trisiloxane.
 8. The coated cellulose and/or syntheticfibre-based support as recited in claim 1, wherein the organic moleculeis present in an amount between 0.1 and 20% by weight of thewater-soluble polymer.
 9. The coated cellulose and/or syntheticfibre-based support as recited in claim 1, wherein the functionalizedwater-soluble polymer is present in an amount of at least 1% by weightof the layer coated onto the fibre-based support.
 10. The coatedcellulose and/or synthetic fibre-based support as recited in claim 1,wherein the layer coated onto the fibre-based support is present in anamount of 0.2 to 20 g/m².
 11. The coated cellulose and/or syntheticfibre-based support as recited in claim 1, wherein the fibres have aweight ranging from 30 to 160 g/m².
 12. A coated cellulose and/orsynthetic fibre-based support produced by a method which comprises thesteps of: (a) forming a cellulose and/or synthetic fibre-based supportsheet with or without a parchementizing process; (b) functionalizing atleast one water-soluble polymer comprising hydroxyl or primary-secondaryamino functional groups by grafting at least one organic moleculecomprising at least one epoxy group and at least one R¹ functional grouponto the water-soluble polymer, wherein R¹ is a vinyl group or at leastone —Si(R²)₃ functional group, where R² is selected from the groupconsisting of hydrogen, hydroxyl, alkoxy, alkyl, and combinationsthereof; (c) coating the cellulose and/or synthetic fibre-based supportsheet obtained according to step (a) with a layer comprising the atleast one functionalized water-soluble polymer obtained according tostep (b) to obtain the coated cellulose and/or synthetic fibre-basedsupport; and (d) optionally calendering or supercalendering the coatedcellulose and/or synthetic fibre-based support.